1. Technical Field:
This invention pertains to semiconductor packaging.
2. Related Art:
Integrated circuits (xe2x80x9cICsxe2x80x9d) are formed on a single die, or xe2x80x9cchip,xe2x80x9d cut from a semiconductor wafer. The dies are relatively small, fragile, susceptible to harmful environmental elements, particularly moisture, and generate a relatively large amount of heat in a relatively small volume during operation. Accordingly, ICs must be packaged in affordable, yet robust packages that protect them from the environment, enable them to be reliably mounted and interconnected with associated electronic components, and effectively dissipate the heat they generate during operation.
The demand for electronic devices that are smaller, yet more functional, has resulted in the development of techniques for incorporating multiple dies in a single package, including techniques for xe2x80x9cstackingxe2x80x9d the dies on top of one another, or alternatively, arrayed in a coplanar relationship on a substrate. Another demand has been for packages in which the back surfaces of the dies can be biased to a specific electrical potential, e.g., ground (xe2x80x9cVssxe2x80x9d), or a supply voltage (xe2x80x9cVccxe2x80x9d).
This invention provides a thin, affordable, small-outline, lead frame semi-conductor package having multiple, generally coplanar dies of the same or different sizes in which the back surfaces of each die can be separately biased to the same or to a different electrical potential. The package includes a plurality of electrically conductive leads held together in a spaced, planar relationship about a central opening defined by the leads, and a plurality of thick, plate-like heat sinks supported within the opening such they are generally coplanar with each other, parallel to the plane of the leads, and electrically isolated from the leads and each other.
Each of the heat sinks has an upper surface with a recess in it and a lower surface that can be exposed through the outer surface of a molded resin envelope encapsulating the package for the efficient dissipation of heat therefrom. A semi-conductor die is mounted in each of the recesses with its back surface in good thermal and electrical connection with the floor of the recess.
Each recess defines a wire bonding ring around the periphery of the upper surface of the respective heat sink immediately adjacent to the edges of the corresponding die for the bonding thereto of conductive wires from the die and/or the leads. The package enables the back surface of each die to be independently biased to the same or a different electrical potential, provides enhanced heat dissipating capabilities and an improved resistance to penetration by moisture, and yields a wire-bonding region that substantially shortens the length of wires bonded thereto and reduces the residual shear stresses acting on the bonds.
The present invention is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings.